I'm So Lost, Black Water?

[DestinyStars]

I left my house for two days on a fishing trip and when I came home my aquarium water is black. Suuuper murky. I thankfully have no fish or plants in it. I checked my filter, it is clean and doesn't seem to be leaking anything strange. All my water perimeters are normal and I've used algae killers just in case but nothing is happening. Has anyone had a problem like this? Sorry if the photo seems dark I tried my best to show the water without catching the reflection. I just don't know what's going on. Edit, I also wanted to say that I've had cloudy water before, but this is like someone replaced my tank water with lake or pond water.

 

[Aqua 59]

How long have you had the tank? Was it just filled up?

 

[DestinyStars]

I've had the tank for 3 years. I did a water change about 4 weeks ago. (I haven't had fish in it for nearly 2 months)